Power system and camera

ABSTRACT

A camera includes: a battery unit on which a battery is mounted, that can be detachably loaded into the camera and supplies power to the camera; and a function unit that executes camera functions, wherein: as a function of the camera is executed, the function unit transmits information related to the executed function to the battery pack; and the battery unit has a storage unit in which the information related to the camera function is stored.

INCORPORATION BY REFERENCE

The disclosures of the following priority applications are hereinincorporated by reference:

-   -   Japanese Patent Application No. 2003-086455 filed Mar. 26, 2003    -   Japanese Patent Application No. 2003-128867 filed May 7, 2003

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a power system used in an apparatussuch as a camera that operates on batteries and also relates to acamera.

2. Description of the Related Art

There are power systems used in cameras in the related art that indicatethe number of photographs that can be taken calculated based upon theremaining battery capacity and the power requirement for taking a singlephotograph. Such power systems include those disclosed in Japanese LaidOpen Patent Publication No. H 10-341536 and Japanese Laid Open PatentPublication No. 2001-154250.

However, a camera power system in the related art such as thosedescribed above cannot calculate the exact remaining number ofphotographs that can be taken on the remaining power when it is adoptedin, for instance, a digital camera, in which the battery power requiredper frame greatly varies depending upon the length of time over whichthe shutter release button is held halfway down, whether or not a strobeis used, the size of the image recorded, whether or not the image isdisplayed at the monitor and the like.

In addition, cameras come equipped with various functions today. Digitalcameras, in particular, offer many functions. However, with a digitalcamera in the related art, a history of consumed battery capacity thathas resulted in the presently remaining battery power level, i.e., whichfunctions of the digital camera have been engaged to lead to thepresently remaining battery power level, cannot be ascertained. If thehistory of the consumed battery capacity in the digital cameraindicating specific functions that have been engaged can be ascertained,it will be possible to generate useful information based upon theconsumed battery capacity history.

SUMMARY OF THE INVENTION

The present invention provides a power system capable of ascertainingwith ease the remaining work volume and the remaining work timeavailable in an apparatus which operates on battery power.

The present invention also provides a camera with which it is possibleto ascertain how the battery power has been consumed.

According to the 1st aspect of the invention, a power system comprises:a battery unit that includes a battery; and an apparatus main body thatoperates on power supplied from the battery in the battery unit mountedthereat, the battery unit and the apparatus main body being engaged ininformation exchange, wherein: a work volume value indicating a volumeof work that the apparatus main body has been engaged in is transmittedfrom the apparatus main body to the battery unit over a predeterminedcycle; the battery unit calculates a cumulative work volume value of thework volume value at the apparatus main body and stores the cumulativework volume value therein, and the battery unit also detects a consumedbattery capacity value indicating an extent to which a battery power hasbeen consumed at the apparatus main body; the cumulative work volumevalue, the consumed battery capacity value and a charged batterycapacity value are transmitted from the battery unit to the apparatusmain body over the predetermined cycle; and the apparatus main bodydisplays a battery use rate indicating an extent to which the batteryhas been used based upon the consumed battery capacity value and thecharged battery capacity value, and also displays the cumulative workvolume value at the apparatus main body.

According to the 2nd aspect of the invention, in the power systemaccording to the 1st aspect, it is preferred that: different operatingmodes of the apparatus main body are classified in correspondence tovarying levels of power consumption; work volume values eachcorresponding to one of the operating modes are transmitted from theapparatus main body to the battery unit; the battery unit calculates andstores therein cumulative work volume values corresponding to theindividual operating modes of the apparatus main body and transmits thecumulative work volume values corresponding to the individual operatingmodes to the apparatus main body; and the apparatus main body displaysthe battery use rate and the cumulative work volume values correspondingto the individual operating modes of the apparatus main body.

According to the 3rd aspect of the invention, in the power systemaccording to the 1st aspect, it is preferred that: the battery unitallows the battery to be charged with a charge apparatus; the batteryunit and the charge apparatus exchange information with each other; andthe cumulative work volume value stored in the battery unit is reset to0 when the battery has been charged by the charge apparatus.

According to the 4th aspect of the invention, in the power systemaccording to the 2nd aspect, it is preferred that: the battery unitallows the battery to be charged with a charge apparatus; the batteryunit and the charge apparatus exchange information with each other; andthe cumulative work volume value stored in the battery unit is reset to0 when the battery has been charged by the charge apparatus.

According to the 5th aspect of the invention, in the power systemaccording to the 1st aspect, it is preferred that: the battery unitallows the battery to be charged with a charge apparatus; the batteryunit and the charge apparatus exchange information with each other; thebattery unit detects the charged battery capacity value and transmitsthe detected charged battery capacity value to the charge apparatus; thecharge apparatus makes a decision based upon the charged capacity valuetransmitted from the battery unit as to whether or not the battery is ina fully charged state and ends a charge of the battery once the batteryis judged to be in the fully charged state; and the battery unit resetsthe consumed battery capacity value stored in memory at the battery unitto 0 when the charge of the battery ends.

According to the 6th aspect of the invention, in the power systemaccording to the 1st aspect, it is preferred that: the apparatus mainbody is a camera; and the work volume value is a number of frames ofimages photographed in the camera.

According to the 7th aspect of the invention, in the power systemaccording to the 1st aspect, it is preferred that: the apparatus mainbody is a camera; and the work volume value is a length of time overwhich the camera has been engaged in use.

According to the 8th aspect of the invention, a camera comprises: abattery unit on which a battery is mounted, that can be detachablyloaded into the camera and supplies power to the camera; and a functionunit that executes camera functions, wherein: as a function of thecamera is executed, the function unit transmits information related tothe executed function to the battery pack; and the battery unit has astorage unit in which the information related to the camera function isstored.

According to the 9th aspect of the invention, in the camera according tothe 8th aspect, it is preferred that: the function unit accumulatesinformation related to the camera functions and transmits theaccumulated information related to the camera functions to the batteryunit; and the storage unit stores therein the accumulated informationrelated to the camera functions having been transmitted.

According to the 10th aspect of the invention, in the camera accordingto the 8th aspect, it is preferred that: the storage unit accumulatesthe information related to the camera function transmitted thereto andstores therein the accumulated information.

According to the 11th aspect of the invention, a camera having loadedtherein a battery unit that includes a battery and a first storage unit,which operates on power supplied from the battery unit, comprises: afunction unit that executes a plurality of functions of the camera; acontrol unit; and a second storage unit, wherein: the second storageunit stores therein cumulative information indicating a value thataccumulate as a function is engaged; and the control unit transmits toand stores into the first storage unit the cumulative information in thesecond storage unit as a first function is engaged, and then resets thecumulative information at the second storage unit; the control unitreads the cumulative information stored in the first storage unit of thebattery unit from the battery unit as a second function is engaged; thecontrol unit obtains a sum of the cumulative information having beenread and cumulative information stored in the second storage unit afterresetting; and the control unit uses the sum of the cumulativeinformation thus obtained as new cumulative information to betransmitted to the battery unit.

According to the 12th aspect of the invention, in the camera accordingto the 11th aspect, it is preferred that: the control unit reads thecumulative information from the first storage unit as a function to beengaged first is engaged and transmits the cumulative information to thefirst storage unit as a function to be engaged last is engaged.

According to the 13th aspect of the invention, in the camera accordingto the 11th aspect, it is preferred that: a plurality of functionsinclude at least one of an image photographing function, a monitordisplay function, a light emitting illumination function, an AF functionand a zoom function; and the cumulative information includes at leastone of a number of images that are photographed, an accumulated timelength of monitor display device ON time, a number of times light hasbeen emitted for illumination, an accumulated length of AF operationtime and an accumulated length of zoom operation time.

According to the 14th aspect of the invention, a camera that operates onpower supplied from a battery unit loaded therein having a chargeablesecondary battery, a measurement unit that measures remaining batterypower value in the secondary battery and a first storage unit in whichthe remaining battery power value is stored, comprises: a function unitthat executes a plurality of functions of the camera; a control unit; asecond storage unit; and a display unit, wherein: the second storageunit stores therein cumulative information indicating values thataccumulate as the functions are engaged; the control unit transmits toand stores into the first storage unit the cumulative information as afirst function is engaged, and then resets the cumulative information atthe second storage unit; the control unit reads the remaining batterypower value and the cumulative information from the battery unit as asecond function is engaged; the control unit reads the remaining batterypower value as each of the plurality of functions is engaged, displaysthe remaining battery power value thus read at the display unit, andobtains a sum of the cumulative information having been read andcumulative information stored in the second storage unit; the controlunit uses the sum of the cumulative information thus obtained as newcumulative information to be transmitted to the battery unit.

According to the 15th aspect of the invention, a camera systemcomprises: a battery unit having a chargeable secondary battery, ameasurement unit that measures remaining battery power value in thesecondary battery and a first storage unit in which the remainingbattery power value is stored; a camera that operates on power suppliedfrom the battery unit loaded therein; and a charge apparatus thatcharges the secondary battery of the battery unit, wherein: the cameraincludes a function unit that executes a plurality of functions of thecamera, a control unit, a second storage unit, and a display unit; thesecond storage unit stores therein cumulative information indicatingvalues that accumulate as the functions are engaged; the control unitreads the remaining battery power value as each of the functions isengaged and displays the remaining battery power value thus read at thedisplay unit; the control unit reads the cumulative information storedin the first storage unit as one of the functions is engaged; thecontrol unit obtains a sum of the cumulative information having beenread and the cumulative information stored in the second storage unit;the control unit transmits the sum to the battery unit for storage andalso resets the cumulative information at the second storage unit asanother function is engaged; and the charge apparatus resets thecumulative information stored in the first storage unit when thesecondary battery in the battery unit has been charged.

According to the 16th aspect of the invention, an electronic apparatussystem comprises: a battery unit having a chargeable secondary battery,a measurement unit that measures remaining battery power value in thesecondary battery and a first storage unit in which the remainingbattery power value is stored; an electronic apparatus that operates onpower supplied from the battery unit loaded therein; and a chargeapparatus that charges the secondary battery of the battery unit,wherein: the electronic apparatus includes a function unit that executesa plurality of functions of the electronic apparatus, a control unit, asecond storage unit, and a display unit; the second storage unit storestherein information that is altered as the functions are engaged; thecontrol unit reads the information stored in the first storage unit asone of the functions is engaged; the control unit generates theinformation with new content based upon the information having been readand the information stored in the second storage unit; the control unittransmits the information with new content to the battery unit forstorage and also resets the information in the second storage unit asanother function is engaged; and the charge apparatus resets theinformation stored in the first storage unit when the secondary batteryin the battery unit has become charged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the structure of the electronic still camera achieved in afirst embodiment;

FIGS. 2A and 2B show the timing with which the camera main body and thesecondary battery unit communicate with each other;

FIG. 3 presents an example of a battery information display;

FIGS. 4A and 4B present flowcharts of the battery information displayprocessing executed at the camera main body and the secondary batteryunit;

FIG. 5 shows the structure adopted in the charger used to charge thesecondary battery unit;

FIG. 6 presents flowcharts of the charge processing executed at thecharger and the secondary battery unit;

FIGS. 7A and 7B schematically illustrate the system configurationadopted in a second embodiment;

FIG. 8 shows the structure of the DSC;

FIG. 9 shows the structure of the charge unit;

FIG. 10 presents the first half of the flowchart of the operationalprocedure at the DSC;

FIG. 11 presents the second half of the flowchart of the operationalprocedure at the DSC;

FIG. 12 presents a flowchart of the photographing mode startupprocessing;

FIG. 13 presents a flowchart of the reproduction mode startupprocessing;

FIG. 14 presents a flowchart of the processing executed on informationrelated to the DSC; and

FIG. 15 presents an example of a display which may be brought up at themonitor display unit to indicate the numbers of pictures that may betaken in correspondence to various photographing conditions.

DESCRIPTION OF PREFERRED EMBODIMENTS First Embodiment

The first embodiment in which the present invention is adopted in anelectronic still camera is now explained. It is to be noted that thepresent invention may be adopted in all types of devices and apparatusesthat operate on secondary batteries (rechargeable batteries).

FIG. 1 shows the structure of the electronic still camera achieved inthe embodiment. A secondary battery unit 30 is mounted at a camera mainbody 10. The secondary battery unit 30 is a detachable unit that can befreely attached to or detached from the camera main body 10. The cameramain body 10 includes a photographic lens 11, an aperture 12, a shutter13, an image-capturing element 14, a CDS•A/D conversion unit 15 thatconverts the output from the image-capturing element 14 to digitalvalues through correlated double sampling, an image processing unit 16,a display control unit 17 that implements control to display a capturedimage, an image display LCD 18, a timing generator that controls thetiming with which the image-capturing element 14 and the CDS•A/Dconversion unit 15 are engaged in operation, a controller 20 thatcontrols the devices and circuits in the image-capturing system, animage memory 21 in which image data are recorded, a motor driver 22, anAF motor 23 that drives a focusing lens at the photographic lens 11, anaperture control actuator 24, a shutter control actuator 25, a cameracontroller 26 that controls the devices and circuits in the photographicsystem, an operation input unit 27 through which operations such as theshutter release operation are input, a display output unit 28 utilizedto display exposure information and the like, a DC/DC converter 29 thatgenerates a voltage needed at the camera and the like.

The secondary battery unit 30 includes a battery controller 31 thatmonitors the consumed battery capacity, the charged battery capacity andthe like, a memory 32 in which a cumulative value indicating a camerause status, the consumed battery capacity, the charged battery capacityand the like are stored, a capacity calculation element 33 that measuresthe consumed battery capacity and the charged battery capacity, batterycells 34, a resistor 35 that detects the consumption current and thecharge current at the battery and the like.

As the secondary battery unit 30 is mounted at the camera main body 10,the battery cells 34 of the secondary battery unit 30 become connectedwith the DC/DC converter 29 at the camera main body 10 via the resistor35 and also, the battery controller 31 and the camera controller 26become connected with each other via a communication line.

In the case of an electronic still camera, the term “camera usestatuses” refers to the statuses of camera operations that need powerfrom the battery unit 30, such as the number of shutter releases, thelength of time over which the power has been in an ON state (the lengthof time over which the camera has been in use), the length of time overwhich the photographic lens has been engaged in focusing operation andthe length of time over which images have been displayed. At least oneof such camera use statuses, e.g., the number of shutter releases, isprovided from the camera controller 26 to the battery controller 31 in apredetermined cycle. At the battery controller 31, a cumulative valuecalculated by using the use statuses having been received is stored inthe memory 32 and the calculated value indicating the use status istransmitted to the camera controller 26.

At the secondary battery unit 30, the capacity calculation element 33detects the consumption current and calculates the battery capacitybeing consumed. As the current, i.e., the consumption current being usedat the camera main body 10, which flows from the battery cells 34 to theDC/DC converter 29 of the camera main body 10, passes through theresistor 35, a voltage (=consumption current×resistance value) isgenerated at the two ends of the resistor 35 in proportion to theconsumption current. Since the capacity of a battery is normallyindicated in units of (mAH) and is defined as the length of time overwhich the battery is capable of continuously supplying a specificcurrent, the consumption current can be detected by measuring thevoltage level at the two ends of the resistor 35, and the batterycapacity being consumed at the camera main body 10 can be ascertainedthrough a time integration of the consumption current. The consumedbattery capacity detected by the capacity calculation element 33 isstored into the memory 32 via the battery controller 31.

The camera controller 26 at the camera main body 10 and the batterycontroller 31 at the secondary battery unit 30 engage in datacommunication over a predetermined cycle, as shown in FIG. 2. The usestatus of the camera main body 10 explained earlier is transmitted fromthe camera main body 10 to the secondary battery unit 30 over a specificcycle, as shown in FIG. 2(a). The use status transmitted from the cameramain body 10 to the secondary battery unit 30 over the specific cyclethrough the data communication is a value corresponding to the timebetween the preceding use status transmission and the present use statustransmission. For instance, if the number of shutter releases istransmitted as the use status, the use status indicates the number ofshutter releases having been performed between the precedingtransmission and the present transmission.

The battery controller 31 adds the use status transmitted from thecamera main body 10 to the secondary battery unit 30 to the use statuscumulative value stored in the memory 32 which was calculated at thetime of previous use status reception. If the number of shutter releaseshas been received as the use status, for instance, the most recentlyreceived number of shutter releases is added to the shutter releasecumulative value stored in the memory 32 calculated at the time of theprevious reception.

After information such as the use status is transmitted from the cameramain body 10 to the secondary battery unit 30, the secondary batteryunit 30 executes processing such as the calculation of the cumulativevalue indicating the cameras use status and the calculation of theconsumed battery capacity, and once the processing is completed, thesecondary battery unit 30 transmits information such as the use statuscumulative value to the camera main body 10. The information transmittedfrom the secondary battery unit 30 to the camera main body 10 includesthe use cumulative value stored in the memory 32, the consumed capacitycalculated at the secondary battery unit 30 and the charged capacity ofthe secondary battery unit 30.

The term “charged capacity” used with respect to the secondary batteryunit 30 refers to the full charged capacity of the secondary batteryunit 30, which may be the rated capacity of the battery cells 34 or maybe indicated by a value obtained by lowering the rated capacity incorrespondence to the extent to which the charge capacity of the batterycells becomes reduced due to battery degradation occurring over time.

For instance, if a value “2” indicating the number of shutter releasesis transmitted from the camera main body 10 to the secondary batteryunit 30 during a communication 1, a value “3” is transmitted during acommunication 2, a value “0” is transmitted during a communication 3 anda value “2” is transmitted during communication 4 in FIG. 2, a shutterrelease cumulative value of 2 is transmitted from the secondary batteryunit 30 to the camera main body 10 during a communication 1′, a shutterrelease cumulated value of 5 is transmitted during a communication 2′, ashutter release cumulative value 5 is transmitted during a communication3′ and a shutter release cumulative value of 7 is transmitted during acommunication 4′.

The cycle over which the camera main body 10 and the secondary batteryunit 30 engage in communication with each other on a regular basis isnormally several seconds. However, some use statuses may be sustainedover longer periods of time than the communication cycle. For instance,the power ON state (length of time over which the camera remains in use)may last over 10 seconds up to several tens of seconds. If a use statusthat is likely to be sustained over a much longer time than the regularcommunication cycle is transmitted through the regular communication, acumulative error may occur. For this reason, a use status such as thepower ON time likely to last longer than the regular communication cyclemay be transmitted over a longer interval than the regular communicationcycle, or it may be transmitted when the power is turned off.

As a battery information display request as issued through the operationinput unit 27, the camera controller 26 at the camera main body 10displays information with regard to the secondary battery unit 30, suchas that shown in FIG. 3, based upon the use status cumulative value, theconsumed battery capacity and the full charged capacity received fromthe secondary battery unit 30. A battery use quantity is displayed asthe ratio (%) of the consumed capacity to the full charged capacity in abar graph. In the example presented in FIG. 3, the ratio of the consumedcapacity to the full charged capacity is indicated as the use quantityin a bar graph, together with a numerical value “35%”.

The shutter release cumulative value “253 frames” and the cumulativepower ON time, i.e., the use time, “35 min 40 sec” corresponding to 35%to which extent the battery has been used after the fully chargedsecondary battery unit 30 was mounted at the camera main body 10, areindicated as use statuses.

Since the battery information in FIG. 3 indicates the number of timesthe shutter has been released in the camera, “253 frames”, and the usetime “35 min 40 sec”, corresponding to a battery use quantity “35%” towhich extent the fully charged battery has become consumed at thepresent time point, the user can correlate the actual performance, i.e.,253 frames of photographed images and over 35 minutes of use, to thebattery use quantity of 35%. Then, based upon the camera use records(work records) corresponding to the battery use quantity representingthe extent to which the fully charged battery has become consumed to thepresent level, the user can easily estimate the number of frames ofimages that can be photographed (the work volume) and the length of timeover which the camera can be engaged in use on the remaining 65% of thebattery power. In other words, by adopting the embodiment, it becomespossible to judge with ease how many more frames of images can bephotographed and how much longer the camera can be used in operation.

FIG. 4 presents flowcharts of the processing executed at the camera mainbody 10 and the secondary battery unit 30 over the predetermined cycle.In reference to these flowcharts, the operations executed at the cameramain body 10 and the secondary battery unit 30 in the embodiment areexplained.

The camera controller 26 at the camera main body 10 executes theprocessing in FIG. 4(a) over the predetermined cycle. In step S1, acamera use status corresponding to the time elapsing between theprevious communication and the present communication with the secondarybattery unit 30, e.g., the number of shutter releases, is transmitted tothe secondary battery unit 30.

The battery controller 31 at the secondary battery unit 30 executes theprocessing in FIG. 4(b) upon receiving the camera use status from thecamera main body 10. After receiving the camera use status correspondingto the time elapsing between the previous communication and the presentcommunication in step S11, the operation proceeds to step S12 to add themost recently received use status to the use status cumulative valuestored into the memory 32 at the time of the previous communication withthe camera main body 10 and stores the sum into the memory 32, therebyupdating the use status cumulative value.

In the following step S13, the consumed battery capacity indicating thebattery capacity having been used over the time elapsing between theprevious communication and the present communication is calculated inthe method explained earlier. Then, the most recently calculatedconsumed capacity is added to the consumed capacity value stored in thememory 32 at the time of the previous communication and the sum isstored into the memory 32, thereby updating the consumed capacity. Instep S14, the present camera use status cumulative value, the consumedbattery capacity and the full charged capacity are read out from thememory 32 and are transmitted to the camera main body 10.

In step S2, the camera controller 26 at the camera main body 10 receivesthe present camera use status cumulative value, the consumed batterycapacity and the full charged capacity from the secondary battery unit30. In the following step S3, the ratio of the present consumed batterycapacity to the battery full charged capacity is calculated to determinethe battery use quantity. In step S4, a verification is executed toascertain whether or not a request to display the information related tothe secondary battery unit 30 has been issued through the operationinput unit 27, and the operation proceeds to step S5 if it is determinedthat a display request has been issued.

In step S5, the battery use quantity, i.e., the ratio of the consumedcapacity to the full charged capacity is indicated with a bar graph anda numerical value (%). In addition, camera use statuses (work records),i.e., the number of shutter releases and the use time (the power ONtime) in this example, indicating how the camera has been engaged inoperation since the fully charged battery unit 30 was mounted at thecamera main body 10 up to the current point, are indicated, as shown inFIG. 3.

Next, an explanation is given on how the secondary battery unit 30 ischarged. FIG. 5 shows the secondary battery unit 30 connected to acharger 40. The charger 40 includes a power circuit 41 which charges thebattery cells 34 at the secondary battery unit 30 and also suppliespower to the charger 40 itself by rectifying an AC source voltage, anindicator device 42 such as an LED that indicates a charge state, acharge controller 43 that manages charge operations by communicatingwith the battery controller 31 at the secondary battery unit 30 and anAC plug 44 through which the connection with the AC source is achieved.

At the secondary battery unit 30 is connected to the charger 40 and theAC plug 44 is connected to and AC source socket (not shown), a charge ofthe battery cells 34 starts. The charge current flowing from the powercircuit 41 at the charger 40 to the battery cells 34 at the secondarybattery unit 30 flows through the resistor 35, thereby generating avoltage (=charge current×resistance value) in proportion to the level ofthe charge current at the two ends of the resistor 35. Thus, as in themeasurement of the consumed capacity as explained earlier, the chargecurrent can be detected by measuring the voltage at the two ends of theresistor 35 while charging the secondary battery unit 30 and the chargedcapacity at the battery cells can be ascertained through timeintegration of the charge current. The charged capacity of the batterycells 34 detected by the capacity calculation element 33 is transmittedto the charge controller 43 of the charger 40 via the battery controller31, and the charge controller 43 manages the charge of the secondarybattery unit 30 by controlling the power circuit 41 based upon thecharged capacity.

As the secondary battery unit 30 is connected to the charger 40, thecharge controller 43 outputs a use status clear command to the memory 32of the battery controller 31. Upon receiving the use status clearcommand, the battery controller 31 resets the use status cumulativevalues indicating the number of shutter releases and the length of powerON time stored in the memory 32 to 0. It is to be noted that the usestatus cumulative values stored in the memory 32 may be reset when thebattery controller 31 detects that the secondary battery unit 30 hasbeen connected to the charger 40, instead.

The charge controller 43 makes a decision as to whether or not thesecondary battery cells 34 have been charged to a fully charged statebased upon the charged capacity value transmitted from the batterycontroller 31, and once the secondary battery cells 34 are determined tobe in a fully charged state, the operation of the power circuit 41 isstopped to end the charge operation and the completion of the chargeoperation is indicated at the indicator device 42. The decision as towhether or not the battery cells have been charged to a fully chargedstate may be made by ascertaining whether or not the charged capacityhas become equal to the consumed capacity. Alternatively, the batterycells may be determined to be in a fully charged state when the chargecurrent has become equal to or smaller than a predetermined value.

Upon the charge completion, the charge controller 43 outputs a consumedcapacity clear command to the battery controller 31 so as to clear theconsumed capacity value stored in the memory 32. Upon receiving theconsumed capacity clear command, the battery controller 31 resets theconsumed capacity value stored in the memory 32 to 0. It is to be notedthat by assuming that the battery cells are to be charged to the fullycharged state once the secondary battery 30 is connected to the charger40, the consumed capacity value in the memory 32 maybe resetautomatically for convenience as the secondary battery unit 30 becomesconnected to the charger 40.

FIG. 6 presents flowcharts of the charge operation executed to chargethe secondary battery unit. (a) shows the processing executed at thecharge controller 43 of the charger 40, whereas (b) shows the processingexecuted at the battery controller 31 of the secondary battery unit 30.

The charge controller 43 at the charger 40 makes a decision in step S21as to whether or not the secondary battery unit 30 has been connected.The secondary battery unit 30 is judged to be connected to the charger40 if an attempted communication with the battery controller 31 isenabled. Once the secondary battery unit 30 is determined to beconnected to the charger 40, the use status clear command is transmittedto the battery controller 31 in step S22.

Upon receiving the use status clear command from the charge controller43, the battery controller 31 of the secondary battery unit 30 resetsthe use status cumulative values stored in the memory 32 to 0 in stepS31.

The charge controller 43 starts charging the battery cells 34 bystarting up the power circuit 41 in step S23. As the charge operationstarts, the battery controller 31 starts measuring the charged capacitywith the capacity calculation element 33 in step S32, and in thefollowing step S33, it transmits the charged capacity ascertainedthrough the measurement to the charge controller 43. It is to be notedthat the charged capacity may be measured over predetermined intervals.

In step S24, the charge controller 43 makes a decision as to whether ornot the battery cells 34 have entered a fully charged state based uponthe charged capacity value transmitted from the battery controller 31.Once it is confirmed that the battery cells have been charged to thefully charged state, the operation proceeds to step S25 to end thecharge executed by the power circuit 41 and the charge completion isindicated at the indicator device 42. Then, in step S26, the consumedcapacity clear command is transmitted to the battery controller 31.

Upon receiving the consumed capacity clear command from the chargecontroller 43, the battery controller 31 resets the consumed capacityvalue stored in the memory 32 to 0 in step S34.

Since the use status cumulative values and the consumed capacity valuestored in the memory 32 at the secondary battery unit 30 are reset to 0every time the secondary battery unit 30 is charged as described above,the measurement of the use status cumulative value and consumed capacitycan start anew for a fully charged secondary battery unit 30 with thefull charged capacity after the fully charged secondary battery unit 30is mounted at the camera main body 10 upon a charge completion, therebyenabling detection of accurate battery information.

As explained above, in the embodiment, the use quantity representing theextent to which the battery has been consumed from the fully chargedstate to the present state relative to the full charged capacity, i.e.,the ratio of battery use and the work volume (the operation volume) withwhich the camera has been engaged in operation from the fully chargedstate to the present state are indicated. As a result, it is possible tojudge with ease and accuracy how much more use the user can expect outof the camera at the present rate of use, i.e., how many more frames ofimages can be photographed and how much longer the camera can be used.Namely, the user can ascertain with ease and accuracy the available work(operation) volume and work (operation) time remaining in an apparatusoperating on a secondary battery.

In addition, since the consumed battery capacity and the camera usestatus cumulative values (apparatus work volume) are stored in thesecondary battery unit 30, accurate battery information can be indicatedeven when the secondary battery unit 30 having been taken out of thecamera is reloaded at the camera.

Furthermore, since the consumed battery capacity and the camera usestatus cumulative values (apparatus work volume) stored at the secondarybattery unit 30 are reset to 0 when the secondary battery unit 30 ischarged, accurate battery information can be detected and indicated.

It is to be noted that an explanation is given above in reference to theembodiment by assuming that the battery cells 34 are charged to thefully charged state during the charge operation and that the chargecapacity value transmitted from the secondary battery unit 30 to thecamera main body 10 is the full charged capacity. However, as theconsumed capacity is stored in the memory 32 of the secondary batteryunit 30 and the exact charged capacity the extent to which the batterycells have been charged can be ascertained during the charge operation,the accurate charged battery capacity can be determined even when thecharge operation is halted before the battery cells become fully chargedfor some reason, by first subtracting the consumed capacity from thefull charged capacity achieved through the previous charge operation,thereby ascertaining the remaining battery capacity, and then by addingthe charged capacity achieved through the present charge operation tothe remaining battery capacity. In such a case, the ratio of theconsumed capacity to the charged capacity at the secondary battery unit30 at the time of the interrupt in the charge operation should beascertained to be indicated with a bar graph and a numerical value (%)at the camera main body 10. Since the use quantity relative to thecharge capacity of the battery unit 30 loaded at the camera after thecharge operation interrupt and the camera use statuses (the camera workvolume) indicating how the camera has been engaged in operation on thepower supplied from the secondary battery unit 30 mounted at the camerafollowing the interrupt in the charge operation can be indicated evenwhen the charged capacity does not match the full charged capacity, theuser can judge with ease and accuracy how much use he will get out ofthe camera at the present rate of use, i.e., how many more pictures hecan take and how much longer he can use the camera.

Alternatively, if the charge operation is interrupted before the batterycells become fully charged, the charged capacity having been achieved bythe time of the charge interrupt may be subtracted from the consumedcapacity stored in the memory 32 of the secondary battery unit 30 so asto determine the ratio of the battery use as the consumed capacityrelative to the full charged capacity as in the embodiment describedearlier.

In the embodiment described above, the consumed battery capacity valueis transmitted from the secondary battery unit 30 to the camera mainbody 10. Instead, the remaining battery capacity maybe determined bysubtracting the consumed capacity from the charge capacity, and theremaining capacity and the charged capacity may be transmitted to thecamera main body 10. In addition, while an explanation is given above inreference to the embodiment on an example in which the ratio of thebattery use is calculated at the camera main body 10 based upon theconsumed battery capacity and the charge capacity, this ratio of batteryuse may instead be calculated at the battery unit 30 and the results ofthe calculation may be provided to the camera main body 10.

In the embodiment described above, the number of photographic frames andthe length of use time (the length of power ON time) are indicated asvalues indicating the work volume that the camera has handled. Asexplained earlier, the level of power consumption in a camera variesdepending upon the specific type of operation it is engaged in, i.e.,depending upon the operating mode. For instance, more power is requiredin the photographing mode in which a photographing operation is executedwhile displaying an image at the monitor or in a reproduction mode inwhich a photographed image is reproduced at the monitor than in aregular photographing mode in which an image is photographed withoutdisplaying the image at the monitor. When indicating the length of timeover which the camera has been engaged in operation after loading acharged battery into the camera, individual lengths of camera operationtime may be indicated separately in correspondence to the mode in whichmuch power needs to be consumed such as a monitor image display mode,and the regular photographing mode so as to allow the user to ascertainhow much time the camera has been engaged in operation in each specificoperating mode. As a result, it becomes possible to judge with ease andaccuracy how long the camera can be used in the operation that the useris planning to perform on the camera.

When the individual lengths of camera or apparatus operation time areindicated for the different operating modes, each operating mode shouldbe classified in correspondence to the specific level of powerrequirement and use status, i.e. the use time, in the operating modeshould be transmitted to the battery unit from the camera or theapparatus so as to enable the battery unit to calculate the cumulativevalues representing the accumulated length of use time for eachoperating mode. Then, the length of use corresponding to the individualoperating modes are transmitted from the battery unit to the camera orthe apparatus, at which the battery use quantity indicating the extentto which the battery has been used since it was loaded in a chargedstate (the ratio of the consumed capacity relative to the chargecapacity), and the lengths of time over which the camera or theapparatus has been engaged in operation in the various operating modesare displayed.

By adopting the embodiment described above, it becomes possible to allowthe user to ascertain with ease and accuracy the remaining work volumeand the remaining work time available in an apparatus that operates on abattery.

Second Embodiment

FIGS. 7A and 7B are schematic block diagrams of structures that may beadopted in the second embodiment of the present invention. Referencenumeral 100 in FIG. 7A indicates a digital camera (hereafter referred toas a DSC), with reference numeral 110 indicating a DSC function unitthat captures a subject image. Reference numeral 200 indicates a batterypack (battery unit) loaded into the DSC 100 to supply power to the DSCfunction unit 110. Reference numeral 300 in FIG. 7B indicates a chargeunit used to charge the battery pack 200. A charging portion 310 of thecharge unit 300 charges the mounted battery pack 200. The battery pack200 is taken out of the DSC 100 and is mounted at the charge unit 300.

FIG. 8 shows in detail the structure adopted in the DSC 100. Thestructural features other than those included in the battery pack 200constitute the DSC function unit 110. The DSC function unit 110comprises an image-capturing unit 411, an image processing unit 411A, amonitor display unit 412, a zoom control unit 413, an AF control unit414, an AE control unit 415, a light emitting illumination unit 416, aninternal storage unit 170, a medium recording/reading unit 180, a powercontrol unit 419, a time count unit 420, a display panel unit 421, asystem CPU (hereafter referred to as a CPU) 430 that is connected withthe individual components and controls the various components and thelike. The image-capturing unit 411 includes a photographic opticalsystem having an aperture, a shutter, a focusing mechanism, a zoommechanism and the like, an image-capturing element and the like. Theimage processing unit 411A generates images by processing signalsprovided by the image-capturing unit 411. The image processing unit 411Agenerates a display image to be displayed at the monitor display unit412 and a recording image to be recorded into the mediumrecording/reading unit 180. The power control unit 419 controls thepower supply from the battery pack 200 to the individual components. TheCPU 430 sets the DSC 100 in a photographing mode, a reproduction mode orthe like, in correspondence to the setting at the mode selector dial(not shown) at the DSC 100. The DSC 100 further includes a groundedelectrical terminal at the area where the battery pack 200 is mounted.

The DSC 100 displays a display image generated by the image processingunit 411A at the monitor display unit 412 in the photographing mode.This display image may be the image currently captured by theimage-capturing element or an image which has already been photographed.The former is used as a view finder image during a photographingoperation. The latter image is displayed immediately after thephotographing operation either automatically or in response to aspecific DSC operation, and the display screen is switched back to theformer image display in response to a specific operation. The latterimage is used to check the photographing results.

The zoom control unit 413 implements control on the drive of the zoommechanism in response to an operation of a zoom switch (not shown) bythe photographer to adjust the magnification factor of the subject imagecaptured at the image-capturing element. The AF control unit 414 adjustsfocus on the subject by controlling the drive of the focusing mechanism.The AE control unit 415 measures the brightness of the subject and setsan aperture value and a shutter speed that will achieve the desiredexposure quantity in conformance to the measured brightness level. Thelight emitting illumination unit 416 emits light and illuminates thesubject when extra light is needed to achieve the desired exposure basedupon the photometering results obtained at the AE control unit 415.

The internal storage unit 170 includes an image buffer 171 and amiscellaneous information storage unit 172. The miscellaneousinformation storage unit 172 is constituted of a nonvolatile memory. Inthe image buffer 171, a recording image generated by the imageprocessing unit 411A in response to a photographing operation executedin the DSC 100 is temporarily stored. The medium recording/reading unit180 records the photographed image temporarily stored in the imagebuffer 171 into a detachable storage medium 181 loaded therein. In themiscellaneous information storage unit 172, various conditions set atthe DSC 100, e.g., basic setting conditions, photographing functionconditions and reproduction function conditions are stored.

The basic setting conditions include, for instance, the ON/OFF settingfor the operation sound, the auto power OFF time setting with which thepower is automatically turn off when no operation has been performedover a specific length of time, the brightness setting for the monitordisplay unit 412 and the ON/OFF settings for displaying various types ofinformation at the monitor display unit 412.

The photographing function conditions include, for instance, the monitordisplay ON/OFF setting, the single AF mode/continuous AF mode, themultiple area photometering/spot photometering/centralized photometeringsetting, the automatic light emission/forced light emission/no lightemission for light emitting illumination, the image quality mode and therecording data size, the white balance condition and the monitor displayON/OFF setting for remaining battery power display. It is to be notedthat in the single AF(S-AF) mode, an auto focus operation is executedonly while the shutter button is pressed halfway down, whereas an autofocus operation is executed at all times while the photographing mode isin effect in the continuous AF(C-AF) mode. The multiple areaphotometering/spot photometering/centralized photometering setting isselected to enable the AE control unit to execute a photometeringoperation in a specific method. The image quality mode and the recordingimage size are set to determine specific image processing conditionsunder which the image processing unit 411A generates a recording image,e.g., the image compression rate and the image size.

The various conditions stored in the miscellaneous condition storageunit are each selected from options corresponding to a given functioncondition. The control unit 430 photographs an image in thephotographing mode or displays a photographic image in the reproductionmode by controlling the various components in conformance to theindividual function condition settings stored in the miscellaneousinformation storage unit 172.

In addition, one of the options corresponding to each condition isstored in the miscellaneous information storage unit 172 as an initialbasic setting condition, an initial photographing function condition oran initial reproduction function condition.

The time count unit 420 is capable of individually counting the lengthsof different types of continuous time periods and various accumulatedtime lengths each representing a cumulative value of a plurality of timeperiods corresponding to a given type.

The DSC 100 reads out an image recorded in the storage medium 181 anddisplays the image thus read out at the monitor display unit 412 in thereproduction mode.

The battery pack 200 includes a secondary battery 201, a measurementunit 202, a means for storage 203, a CPU 204, a charge/discharge controlunit 206 and an indicator unit 207. The secondary battery 201 is arechargeable battery which may be, for instance, a lithium ion battery,a nickel hydrogen battery or a nickel cadmium battery. In the means forstorage 203, information indicating the remaining battery power (ratedvalue) when the secondary battery 201 is in a fully charged state, theremaining battery power at the end of a charge operation, the remainingbattery power currently available in the battery (hereafter may besimply referred to as the remaining battery power) and the like isstored. The CPU 204 to which the measurement unit 202, the means forstorage 203, the charge/discharge control unit 206 and the indicatorunit 207 are connected, is driven by the secondary battery 201. Themeasurement unit 202 measures the voltage and the current output fromthe secondary battery 201 or the voltage and the current input to thesecondary battery 201, as well as the battery temperature.

The CPU 204, which also functions as part of the measurement unit 202,calculates the quantity of electricity flowing out from the secondarybattery 201 based upon the output voltage and the output current,calculates the quantity of electricity flowing into the secondarybattery 201 based upon the input voltage and the input current,determines a new value indicating the remaining battery power, i.e., thequantity of electricity that can be output subsequently, based upon thepresent value of the remaining battery power stored in the means forstorage 203 and the quantities of electricity outflow/inflow, andupdates the remaining battery power at the means for storage 203 withthe new value for the remaining battery power. The remaining batterypower is calculated by incorporating a temperature compensation basedupon the battery temperature measured by the measurement unit 202, sincethe remaining battery power value increases as the battery temperaturerises and decreases as the battery temperature falls. In addition, theratio of the current remaining battery power to the remaining batterypower when the secondary battery 201 is in the fully charged state,i.e., the charge rate, is determined to update the outstanding chargerate stored in memory.

The charge/discharge control unit 206 starts/stops the power supply fromthe secondary battery 201 to the outside and a charge of the secondarybattery 201 in response to commands issued from the CPU 204.

At the indicator unit 207, the state of the battery pack 200 and thelike are indicated in response to a command from the CPU 204. The stateof the battery pack 200 includes the remaining battery power and thecharge rate mentioned earlier.

The battery pack 200 further includes a means for mount detection 205that is utilized to detect the apparatus into which the battery pack 200is mounted. The means for mount detection 205 has an electrical terminalwhich is connected to an electrical terminal of the apparatus at whichthe battery pack 200 is mounted and detects the potential at theelectrical terminal. Based upon the detected potential, the CPU 204detects the apparatus into which the battery pack 200 has been loaded.The grounded electrical terminal at the DSC 100 is connected to theelectrical terminal of the means for mount detection 205.

The CPU 204 at the battery pack 200 and the CPU 430 at the DSC 100 intowhich the battery pack 200 is mounted exchange various types ofinformation. The CPU 430 obtains the information indicating theremaining battery power stored at the means for storage 203 via the CPU204 and displays the obtained information at the display panel unit 421.Depending upon the display condition set at the DSC 100, the informationmay also be displayed at the monitor display unit 412. The informationdisplayed at the monitor display unit 412 may be superimposed over adisplay image.

FIG. 9 shows in detail the charge unit 300. The charging portion 310 atthe charge unit 300 includes a charge circuit 311, a charge control unit312 and a CPU 313. The CPU 313 issues commands for the charge controlunit 312 to control the charge circuit 311 and also exchanges varioustypes of communication with the CPU 204 at the battery pack 200 mountedat a specific position of the charge unit 300. The battery pack 200mounted at the specific position of the charge unit 300 is charged bythe charging portion 310. The charge circuit 311 receives power from acommercial source and supplies a voltage/current suitable for chargingthe secondary battery 201 to the battery pack 200. The charge controlunit 312 includes an electrical terminal which is connected to theelectrical terminal of the means for mount detection 205 at the batterypack 200 mounted at the charge unit 300. A predetermined level ofpotential is achieved at the electrical terminal of the charge controlunit 312.

The CPU 204 of the battery pack 200 constantly monitors the electricalpotential at the electrical terminal of the means for mount detection205 over a predetermined cycle. If the detected potential is 0 V, theCPU 204 judges that the battery pack is mounted in the DSC 100, whereasit judges that the battery pack 200 is mounted at the charge unit 300 ifthe detected potential is at the predetermined level. If no potential isdetected, the CPU 204 judges that the battery pack 200 is not mounted atany apparatus. If the battery pack 200 is judged to be loaded in the DSC100, the CPU 204 issues a command for the charge/discharge control unit206 to start power supply from the secondary battery 201. To be moreprecise, the actual power supply starts when the power switch at the DSC100 is turned on. If the battery pack 200 is judged to be mounted at thecharge unit 300, the CPU 204 issues a command for the charge/dischargecontrol unit 206 to enable a charge of the secondary battery 201. Sincethe detection and judgment are executed constantly, the CPU 204 is ableto sense a disengagement of the battery pack from the apparatus at whichthe battery pack 200 has been mounted, as well. Then, its stores theremaining battery power at the time of the disengagement into the meansfor storage 203 as the remaining battery power at the charge end.Subsequently, it issues a command for the charge/discharge control unit206 to cut off the terminal used for power supply/charge from theinternal circuits of the battery pack 200, thereby disabling the powersupply/charge. As a result, it is possible to prevent shorting.

Next, the internal operation of the DSC 100 is explained by focusing onthe processing executed by the CPU 430. FIGS. 10 and 11 present aflowchart of the processing executed at the CPU 430. While the procedureshown in FIG. 10 and the procedure shown in FIG. 11 are both part of asingle procedural sequence, they are presented in two separate drawingsfor convenience. The explanation is first given in reference to FIG. 10.The processing in FIG. 10 starts as the power switch at the DSC 100 isturned on.

In step S101, the remaining battery power R is read from the means forstorage 203 at the battery pack 200. At the same time, the remainingbattery power at the charge end is also read and stored into themiscellaneous information storage unit 172. If a value representing theremaining battery power is already stored in the miscellaneousinformation storage unit 172, the value is updated. It is to be notedthat the read of the DSC information indicated inside the parentheses ofstep 101 is to be explained in detail later.

In step S102, a decision is made as to whether or not the remainingbattery power R having been read is equal to or greater than a firstpredetermined value at which at least some of the functions of the DSC100 can be engaged in operation. If it is decided that the remainingbattery power R is equal to or greater than the first predeterminedvalue, the operation proceeds to step S103, whereas the operationproceeds to step S113 if the remaining battery power is determined to beless than the first predetermined value. After an error message such as“insufficient battery power” is displayed over a predetermined length oftime in step S113, the power switch is turned off in step S114 and thenthe processing ends.

In step S103, the various components of the DSC 100 are set to the basicinitial settings. The basic initial setting conditions stored in themiscellaneous information storage unit 172 are used as the basic initialsettings. A basic initial setting condition selected as an initialsetting of the DSC 100 can be altered by performing a specific operationat the DSC 100. Then, by performing a further specific operation, thebasic initial setting condition stored in the miscellaneous informationstorage unit 172 is updated to the new condition setting.

In step S104, the time count unit 420 starts a first time count. In thefirst time count, the time count unit 420 measures the length of timeover which the DSC 100 is engaged in operation (the DSC operation time).The time count of the DSC operation time continues until the powerswitch of the DSC 100 is turned off. A further explanation is given inreference to FIG. 11.

In step S105, the mode having been set through the mode selector dialwhich is operated to select an operating mode for the DSC 100 is judgedand the operation proceeds to execute the processing corresponding tothe specific mode setting. For instance, if the photographing mode hasbeen set in the DSC, the operation proceeds to step S106, whereas if thereproduction mode has been set, the operation proceeds to step S116.

In step S106, the DSC 100 is started up in the photographing mode. Theprocessing executed in step S106 is to be described in detail later.

In step S107, the DSC 100 executes photographing mode processing, i.e.,it executes the various functions needed to photograph images inresponse to a DSC operation performed by the photographer.

In step S108, a decision is made as to whether or not the photographingmode is to be sustained. If the photographing mode is still set at themode selector dial, the photographing mode is judged to be still ineffect and accordingly, the operation returns to step S107 to continuewith the photographing mode processing. If, on the other hand, it isdecided that the photographing mode is no longer in effect, theoperation proceeds to step S109. It is judged that the photographingmode is no longer in effect if the mode selector dial setting has beenchanged to another mode, e.g., the reproduction mode.

In step S109, photographing mode end processing is executed. Processingsimilar to that executed to exit the photographing mode in a DSC in therelated art is executed as the photographing mode end processing. Sincethe details of this processing are of the known art, their explanationis omitted. It is to be noted that if the power switch of the DSC 100 isturned off in the photographing mode, the processing in step S109 isexecuted in response to an interrupt command 50 generated and input inresponse to the power OFF.

In step S110, a decision is made as to whether or not the power switchhas been turned off, i.e., whether or not the interrupt command 50 hasbeen input. If an interrupt command has been input, the operationproceeds to step S130 to execute end processing similar to that executedin DSCs in the related art and turn off the power. Otherwise, theoperation returns to step S105 after reading the remaining battery powerR in step S111, to engage in startup processing for the mode newlyselected through the mode selector dial. For instance, if the setting atthe mode selector dial has been switched to the reproduction mode, theoperation proceeds to step S116.

If, on the hand, it is judged in step S105 that the reproduction mode isset at the mode selector dial, the DSC 100 is started up in thereproduction mode in step S116. The processing executed in step S116 isto be described in detail later.

Instep S117, the DSC 100 executes the reproduction mode processing,i.e., it executes various functions related to photographic imagereproduction in response to a DSC operation performed by thephotographer.

In step S118, a decision is made as to whether or not the reproductionmode is to be sustained. If the mode selector dial is still set at thereproduction mode, it is judged that the reproduction mode is to besustained, and the operation returns to step S117 to continuouslyexecute the reproduction mode processing. If, on the other hand, it isjudged that the reproduction mode is no longer in effect, the operationproceeds to step S119. It is judged that the reproduction mode is nolonger in effect if the setting at the mode selector dial has beenswitched to another mode such as the photographing mode.

In step S119, reproduction mode end processing is executed. Processingsimilar to that executed to exit the reproduction mode in a DSC in therelated art is executed as the reproduction mode end processing. Sincethe details of this processing are of the known art, their explanationis omitted. It is to be noted that if the power switch of the DSC 100 isturned off in the reproduction mode, the processing in step S119 isexecuted in response to an interrupt command 50 generated and input inresponse to the power OFF.

In step S120, a decision is made as to whether or not the power switchhas been turned off. If the power switch is judged to have been turnedoff, the operation proceeds to step S130 to execute end processing byturning off the power. The end processing is to be described in detaillater. Otherwise, after reading the remaining battery power R in stepS121, the operation returns to step S105 to execute startup processingfor the new mode selected with the mode selector dial. For instance, ifthe photographing mode has been selected with the mode selector dial,the operation proceeds to step S106.

The procedure of the photographing mode startup processing executed instep S106 and the procedure of the reproduction mode startup processingexecuted in step S116 are respectively shown in FIGS. 12 and 13.

It is to be noted that instead of or in addition to reading theremaining battery power in steps S111 and S121, the remaining batterypower R may be read at the end of each type of processing or at the endsof certain types of processing executed in the photographing mode or thereproduction mode, which requires a great deal of battery power, e.g.,photographing processing executed in response to a full-press operationof the shutter button and a light emission at the light emittingillumination unit 416 in the photographing mode, and display imageselection processing in the reproduction mode. In such a case, a higherlevel of accuracy is achieved in the remaining battery power displaywhich is to be explained in reference to FIGS. 12 and 13. Upon startingthe photographing mode startup processing in FIG. 12 (step S106 in FIG.11), the CPU 430 executes initial setting for photographing modeinitialization instep S201. The initial photographing functionconditions stored in the miscellaneous information storage unit 172 areused as the initial settings in the photographing mode. As explainedearlier, the photographing function conditions include the monitordisplay ON/OFF setting, the single AF mode/continuous AF mode setting,the multiple area photometering/spot photometering/centralizedphotometering setting, the automatic light emission/forced lightemission/no light emission setting for light emitting illumination, theimage quality mode and the recording data size, the white balancecondition and the monitor display ON/OFF setting for the remainingbattery power display. In this example, the first option among theoptions for each condition distinguished from each other with a “/” isstored in the miscellaneous information storage unit 172 as the initialphotographing function condition.

A given photographic function condition selected as an initial settingat the DSC 100 can be altered through a subsequent specific operationperformed at the DSC 100 in the photographing mode. Then, by performinga further specific operation, the initial photographing functioncondition stored in the miscellaneous information storage unit 172 isupdated to the new condition setting.

In step S202, the DSC 100 is started up in conformance to thephotographing function conditions selected as the initial settings asexplained above. At this time, the monitor display unit 412 is set in anON state or an OFF state depending upon the monitor display unit ON/OFFcondition which is one of the photographing function conditions and theremaining battery power R. Namely, a decision is made as to whether themonitor display unit ON setting or the monitor display unit OFF settingis currently selected. If the ON setting is in effect, the operationproceeds to step S204, whereas if the OFF setting is in effect, theoperation proceeds to step S207.

Instep S204, a decision is made based upon the remaining battery power Rread in step S101 in FIG. 10 or in step S111 or step S121 in FIG. 11.The remaining battery power R read in step S111 or S121 in FIG. 11 islower than the remaining battery power R read in step S101 in FIG. 10,since the battery power is further consumed in the DSC 100 between stepS101 and step S111 or between step S101 and step S121.

The operation proceeds to step S205 if the remaining battery power R isequal to or greater than a second predetermined value indicating thebattery power needed to photograph an image by engaging the monitordisplay unit 412, whereas the operation proceeds to step S225 if theremaining battery power R is less than the second predetermined valuebut it is equal to or greater than a third predetermined valueindicating the battery power with which an image can be photographed aslong as the monitor display unit 412 is not engaged to turn off themonitor display unit 412 and then a message indicating that the batteryno longer has enough power to enable a photographing operation performedby engaging the monitor display unit 412 is brought up at the displaypanel unit 21 in step S226 before the operation proceeds to step S207.It is to be noted that the second predetermined value is larger than thefirst predetermined value mentioned earlier. If the remaining batterypower R is determined to be less than the third predetermined value, theoperation proceeds to step S215 to turn off the monitor display unit 412and then, in step S216, an error message is displayed to indicate that aphotographing operation is disabled due to insufficient battery power isdisplayed at the display panel 21 before the processing ends.

In step S205, the time count unit 420 starts a second time count. In thesecond time count, the accumulated length of time (accumulated monitorON time) over which the monitor display unit 412 is engaged in operation(monitor ON time) is measured. The monitor ON time is measured (themonitor ON count is sustained) until the photographing mode ends oruntil the power switch of the DSC 100 is turned off. If the monitordisplay unit 412 is turned off in the photographing mode, the monitor ONcount is halted, and then the time count is resumed as the monitordisplay unit 412 is turned on again so as to measure the accumulatedmonitor ON time.

As explained later, the length of time over which the monitor displayunit is set in an ON state is also measured during the reproduction modeprocessing. The accumulated length of time over which the monitordisplay unit remains in an ON state includes the monitor ON timemeasured during the reproduction mode processing as well. Namely, thecumulative value represents the overall length of time over which themonitor is in an ON state after the power switch of the DSC 100 isturned on.

Instep S206, the remaining battery power R is displayed at the monitordisplay unit 412.

Instep S207, the remaining battery power R is displayed at the displaypanel unit 21.

After executing the photographing mode startup procedure describedabove, the photographing mode processing in step S107 in FIG. 11 isexecuted.

The photographing mode processing (executed in step S107 in FIG. 11) isnow explained. During the photographing mode processing, processingsimilar to that executed during a photographing operation in a DSC inthe related art is executed. While the processing which is of the knownart is not explained in detail, an image captured by the image-capturingunit 411, for instance, is displayed in real time at the monitor displayunit 412 during the photographing mode processing. This display image isused as a view finder image. If the monitor display OFF setting has beenselected, the display image is not displayed.

As the shutter button (not shown) at the DSC is pressed halfway down, AFprocessing and photometering processing are respectively executed by theAF control unit 414 and the AE control unit 415, and in response to afull-press operation of the shutter button, photographing processing isexecuted. Namely, in response to a halfway press operation of theshutter button, the focus is adjusted on to the subject by the AFcontrol unit 414, the AE control unit 415 sets the aperture and theshutter speed to values selected based upon the results of thephotometering processing and light is emitted at the light emittingillumination unit 416 as necessary. In addition, a recording imagetogether with a display image for reproduction and a thumbnail imagecorresponding to the recording image is generated at the imageprocessing unit 411A by using the image photographed in response to afull-press operation of the shutter button, and the images are storedinto the image buffer 171 and are also recorded into the recordingmedium 181 at the medium recording/reading unit 180. The recording imageis an image having undergone processing executed at the image qualitymode setting, the recording data size setting and the white balancecondition setting selected as part of the photographing functionconditions explained earlier. The reproduction display image is asmall-size image generated in conformance to the performance level ofthe monitor display unit 412 and the thumbnail image is an even smallerimage for thumbnail display.

It is to be noted that if the remaining battery power R is read at theend of each type of processing or at the ends of certain types ofprocessing executed in the photographing mode processing or thereproduction mode processing, the processing in step S204 and subsequentsteps in FIG. 12 or the processing in step S303 and subsequent steps inFIG. 13, too, should be executed each time the remaining battery power Ris read.

Upon starting the reproduction mode startup processing in FIG. 13 (stepS116 in FIG. 11), the CPU 430 executes initial setting for theinitialization for the reproduction mode in step S301. The initialreproduction function conditions stored in the miscellaneous informationstorage unit 172 are used as the initial settings in the reproductionmode. The reproduction function conditions include the number of imagesto be brought up on display together in thumbnail image display and thelength of time intervals over which a plurality of images are to bereproduced continuously, for example. An initial reproduction functioncondition selected as an initial setting at the DSC 100 can be alteredby performing a subsequent specific operation performed at the DSC 100in the reproduction mode. Then, by performing a further specificoperation, the initial reproduction function condition stored in themiscellaneous information storage unit 172 is updated to the newcondition setting.

In step S302, the DSC 100 is started up in conformance to thereproduction function conditions selected as the initial settings asexplained above. At this time, the monitor display unit 412 is set in anON state or an OFF state depending upon the remaining battery power R.Namely, in step S303, a decision is made as to whether or not theremaining battery power R read in step S101 in FIG. 10 or in step S111or step S121 in FIG. 11 is equal to or greater than a fourthpredetermined value indicating the battery power that enables theexecution of the operation in the reproduction mode. The remainingbattery power R read in step S111 or S121 in FIG. 11 is lower than theremaining battery power R read in step S101 in FIG. 10, since thebattery power is further consumed in the DSC 100 between step S101 andstep S111 or between step S101 step S121. The operation proceeds to stepS304 if the remaining battery power is determined to be equal to orgreater than the fourth predetermined value, whereas the operationproceeds to step S3014 if it is judged to be less than the fourthpredetermined value.

In step S304, the time count unit 420 starts a second time count, i.e.,the time count of the accumulated length of monitor ON time. The monitorON time is measured (the monitor ON count is sustained) until thereproduction mode ends or until the power switch of the DSC 100 isturned off.

As explained earlier, the length of time over which the monitor displayunit remains in an ON state is also measured during the photographingmode processing. The accumulated length of time over which the monitordisplay unit is in an ON state includes the monitor ON time measuredduring the photographing mode processing, as well. Namely, thecumulative value represents the overall length of time over which themonitor is in an ON state after the power switch of the DSC 100 isturned on.

In step S305, the remaining battery power R is displayed at the monitordisplay unit 412.

In step S306, the remaining battery power R is displayed at the displaypanel unit 21.

By executing the reproduction mode startup procedure described above,the DSC 100 is set in a photographic image reproduction enabled state.

The following processing is executed if the remaining battery power R isjudged to be less than the fourth predetermined value in step S303.

The monitor display unit 412 is turned off in step S314, and theremaining battery power R is displayed at the display panel unit 21 instep S315. In step S316, an error message indicating that the remainingbattery power is insufficient is displayed before the processing ends.

Next, the reproduction mode processing (executed in step S117 in FIG.11) is explained. During the reproduction mode processing, processingsimilar to that executed during a reproduction operation in a DSC in therelated art is executed. While the processing which is of the known artis not explained in detail, an image recorded in the storage medium 181,for instance, is read out and displayed at the monitor display unit 412.At this time, the specific number of thumbnail images generated incorrespondence to individual recording images, which number is set as areproduction function condition, is displayed at once. The user is thenprompted to select any image among the thumbnail images by performing aspecific operation and then the reproduction image corresponding to theselected image is brought up on display. In addition, a flag indicatingwhether or not the recording image corresponding to the display imageneeds to be printed can be set. The photographing conditions under whichthe image on display was photographed and the like may be superimposedon the display as well.

Information related to the DSC is stored in the means for storage 203 inthe embodiment. The DSC-related information is stored by the CPU 430during the end processing executed in the DSC 100. The DSC-relatedinformation includes the accumulated length of time over which theshutter button has been pressed halfway down, the number of photographshaving been taken, the number of times at which light has been emittedat the light emitting illumination unit 416, the accumulated length oftime over which the zoom has been engaged, the length of time over whichthe monitor has been in an ON state and the length of time over whichthe DSC has been engaged in operation. It is to be noted that theDSC-related information is stored at the means for storage 203 is resetwhen the secondary battery 201 becomes charge to a sufficient extent,e.g., to an extent equal to or greater than the charge rate of 85%.Then, the CPU 430 at the DSC 100 executes processing such as that shownin FIG. 14 on the DSC-related information. Namely, the DSC-relatedinformation is read out from the means for storage 203 and is storedinto the miscellaneous information storage unit 172 as read informationin step S401. This processing is executed when reading the remainingbattery power in step S101 in FIG. 10.

Instep S402, the time count unit 420 measures the length of time overwhich the shutter button has been pressed halfway down (halfway presstime), and the cumulative value indicating the accumulated length oftime over which the shutter button has been pressed halfway down isstored into the miscellaneous information storage unit 172 as mostrecent information. It is desirable to include the length of time overwhich the shutter button has been pressed all the way down in theaccumulated halfway press time. The cumulative value may be calculatedby, for instance, the CPU 430. It is to be noted that if the continuousAF mode setting has been selected as a photographing function condition,the accumulated length of time over which the photographing mode hasbeen sustained is stored into the miscellaneous information storage unit172, as well.

In addition, the number of times the shutter button has been pressed allthe way down, i.e., the number of photographs taken, is counted and thecount value is stored into the miscellaneous information storage unit172 as most recent information. The number of times at which light hasbeen emitted at the light emitting illumination unit 416 is also countedand the count value is stored into the miscellaneous information storageunit 172 as most recent information. The time count unit 420 measuresthe length of time over which the zoom control unit for 13 has beenengaged in operation (zoom operation time) and the value indicating theaccumulated length of time over which the zoom control unit has beenengaged in operation is stored into the miscellaneous informationstorage unit 172 as most recent information.

The storage of the most recent information is executed whenevernecessary as various operations are performed at the DSC 100 and thevarious functions of the DSC 100 are engaged. However, the accumulatedlength of halfway press time and the accumulated length of zoomoperation time may be simply measured at the time count unit 420.

In step S403, the sums of the values indicated in the information havingbeen read and the values indicated in the most recent information areobtained as present information indicating the present state of the DSC.

The processing in steps S402 and S403 is executed concurrently with thephotographing mode processing in step S107 in FIG. 11 and thereproduction mode processing in step S117 in FIG. 11.

In step S404, a decision is made as to whether or not the power switchhas been turned off, and the operation returns to step S402 if it isdecided that the power switch has not been turned off whereas theoperation proceeds to step S405 if it is decided that the power switchhas been turned off.

In step S405, the present information is provided to the CPU 204 at thebattery pack 200. Then, the present information is used to update theDSC-related information stored in the means for storage 203 via the CPU204.

In step S406, the values having been measured at the time count unit 420and the values stored in the miscellaneous information storage unit 172are all reset to 0.

The processing in steps S405 and S406 is executed concurrently with theend processing in step S130 in FIG. 11.

Since the DSC-related information stored at the battery pack 200 isreset as the secondary battery 201 becomes charged, the DSC-relatedinformation stored at the means for storage 203 indicates theaccumulated length of halfway press time, the number of photographshaving been taken, the number of times at which light has been emittedat the light emitting illumination unit 416, the accumulated length ofzoom operation time, the length of time over which the monitor has beenon and the length of time over which the DSC has been engaged inoperation after the battery pack 200 was charged most recently.

The DSC 100 executes processing by using the DSC-related information toprovide various types of information useful to the user of the DSC 100.This processing is to be described in detail later.

It is to be noted that the remaining battery power R alone may beinitially read and the DSC-related information may be read only if theremaining battery power R is judged to be equal to or greater than thefirst predetermined value or the third predetermined, instead.

An example of the useful information that may be provided to the user ofthe DSC 100 based upon the DSC-related information is now explained.

The CPU 430 reads the remaining battery power R in response to aspecific operation performed at the DSC 100. Then, based upon consumedbattery power ascertained in correspondence to the remaining batterypower at the charge end read in step S101 in FIG. 10 and the remainingbattery power R and the number of photographs having been takenindicated in the present information, the consumed battery capacityquantity (performance value) per single photographed image iscalculated. And a number of photographs that can be taken is estimatedby using the consumed battery capacity quantity per single photographedimage and is displayed at the monitor display unit 412. The estimatedvalue is stored into the means for storage 203 via the CPU 204 of thebattery pack 200 and it also is indicated at the indicator unit 207.Thus, the user can ascertain the estimated number of photographs thatcan be taken by checking the value indicated at the indicator unit 207,even when the battery pack 200 is disengaged from the DSC 100. If theuser has a plurality of battery packs, he can choose a battery pack witha sufficient level of battery power remaining to take the desired numberof pictures.

The battery power needed to photograph a single image fluctuatesdepending upon the length of time over which the display monitor 412remains in an ON state while photographing the image (which is affectedby the length of time required to determine the composition and thelength of time required to check the photographic image), the length oftime over which the shutter button is held halfway down (correspondingto the length of time over which the AF operation is executed), thelength of time over which the zoom operation is executed and the like.These time lengths and the frequency with which the correspondingcomponents are engaged in operation tend to vary among individualphotographers. The need to emit light with the light emittingillumination unit 416 arises when photographing images at a specifictime of day or under specific lighting conditions. For this reason, aslong as a given photographer keeps taking photographs with aphotographing pattern similar to the previous photographing pattern, thebattery power needed to photograph a single image does not change much.Under such circumstances, the estimated value will prove useful to theuser.

While the number of images that can be photographed may be calculatedbased upon the theoretical power consumption quantity corresponding tothe standard photographing behavior pattern anticipated by the digitalcamera manufacturer, the estimated value obtained based upon the actualnumber of photographed images and the corresponding consumed batterypower (the performance value) in the embodiment described above achievesa higher degree of accuracy by reflecting the photographing behaviorpattern of the specific photographer.

The CPU 430 reads and checks the remaining battery power R when thepower to the DSC 100 is turned on. The CPU 430 calculates the estimatedvalue at this point, too, if the remaining battery power R is less thana predetermined value and displays the estimated value at the monitordisplay unit 412 and the display panel unit 21 to warn the user that thebattery power R is running low. It will be particularly effective towarn the user by superimposing the estimated value over a photographicimage displayed at the monitor display unit 412. If the remainingbattery power is equal to or greater than the predetermined value, theprocessing ends without estimating the number of images that can bephotographed, since a sufficient level of battery power is stillavailable and the user can take photographs without worrying about thebattery power running low.

In addition, the number of images that can be photographed is alsoestimated in the end processing (executed in step S130 in FIG. 11). Itis desirable to provide a non-visual warning such as a warning sound ora warning vibration together with the display of the number of imagesthat can be photographed. Since the user can verify how many more imageas can be taken on the remaining battery power when ending use of theDSC 100, he is able to make an accurate judgment as to whether or notthe battery pack 200 needs to be charged before he next uses the DSC100. Thus, the user can prevent a trouble in which he can not perform adesired photographing operation due to a depleted battery when he isready to use the DSC 100. It is desirable to indicate the number ofimages that can be photographed having been estimated during the endprocessing at the indicator unit 207 as described earlier, regardless ofwhether a large number of images or a small number of images can bephotographed on the remaining battery power. Moreover, the number ofimages that can be photographed having been estimated during the endprocessing may be indicated at an indicator unit 207 of a battery pack200 which is used in a silver halide film camera instead of a DSC, byadopting the processing principal explained above, to achieve similaradvantages.

FIG. 15 presents an example of a display that may be brought up at themonitor display unit to indicate varying numbers of images that can bephotographed under different photographing conditions.

The above described embodiments are examples, and various modificationscan be made without departing from the spirit and scope of theinvention.

1. A power system comprising: a battery unit that includes a battery;and an apparatus main body that operates on power supplied from thebattery in the battery unit mounted thereat, the battery unit and theapparatus main body being engaged in information exchange, wherein: awork volume value indicating a volume of work that the apparatus mainbody has been engaged in is transmitted from the apparatus main body tothe battery unit over a predetermined cycle; the battery unit calculatesa cumulative work volume value of the work volume value at the apparatusmain body and stores the cumulative work volume value therein, and thebattery unit also detects a consumed battery capacity value indicatingan extent to which a battery power has been consumed at the apparatusmain body; the cumulative work volume value, the consumed batterycapacity value and a charged battery capacity value are transmitted fromthe battery unit to the apparatus main body over the predeterminedcycle; and the apparatus main body displays a battery use rateindicating an extent to which the battery has been used based upon theconsumed battery capacity value and the charged battery capacity value,and also displays the cumulative work volume value at the apparatus mainbody.
 2. A power system according to claim 1, wherein: differentoperating modes of the apparatus main body are classified incorrespondence to varying levels of power consumption; work volumevalues each corresponding to one of the operating modes are transmittedfrom the apparatus main body to the battery unit; the battery unitcalculates and stores therein cumulative work volume valuescorresponding to the individual operating modes of the apparatus mainbody and transmits the cumulative work volume values corresponding tothe individual operating modes to the apparatus main body; and theapparatus main body displays the battery use rate and the cumulativework volume values corresponding to the individual operating modes ofthe apparatus main body.
 3. A power system according to claim 1,wherein: the battery unit allows the battery to be charged with a chargeapparatus; the battery unit and the charge apparatus exchangeinformation with each other; and the cumulative work volume value storedin the battery unit is reset to 0 when the battery has been charged bythe charge apparatus.
 4. A power system according to claim 2, wherein:the battery unit allows the battery to be charged with a chargeapparatus; the battery unit and the charge apparatus exchangeinformation with each other; and the cumulative work volume value storedin the battery unit is reset to 0 when the battery has been charged bythe charge apparatus.
 5. A power system according to claim 1, wherein:the battery unit allows the battery to be charged with a chargeapparatus; the battery unit and the charge apparatus exchangeinformation with each other; the battery unit detects the chargedbattery capacity value and transmits the detected charged batterycapacity value to the charge apparatus; the charge apparatus makes adecision based upon the charged capacity value transmitted from thebattery unit as to whether or not the battery is in a fully chargedstate and ends a charge of the battery once the battery is judged to bein the fully charged state; and the battery unit resets the consumedbattery capacity value stored in memory at the battery unit to 0 whenthe charge of the battery ends.
 6. A power system according to claim 1,wherein: the apparatus main body is a camera; and the work volume valueis a number of frames of images photographed in the camera.
 7. A powersystem according to claim 1, wherein: the apparatus main body is acamera; and the work volume value is a length of time over which thecamera has been engaged in use.
 8. A camera comprising: a battery uniton which a battery is mounted, that can be detachably loaded into thecamera and supplies power to the camera; and a function unit thatexecutes camera functions, wherein: as a function of the camera isexecuted, the function unit transmits information related to theexecuted function to the battery pack; and the battery unit has astorage unit in which the information related to the camera function isstored.
 9. A camera according to claim 8, wherein: the function unitaccumulates information related to the camera functions and transmitsthe accumulated information related to the camera functions to thebattery unit; and the storage unit stores therein the accumulatedinformation related to the camera functions having been transmitted. 10.A camera according to claim 8, wherein: the storage unit accumulates theinformation related to the camera function transmitted thereto andstores therein the accumulated information.
 11. A camera having loadedtherein a battery unit that includes a battery and a first storage unit,which operates on power supplied from the battery unit, comprising: afunction unit that executes a plurality of functions of the camera; acontrol unit; and a second storage unit, wherein: the second storageunit stores therein cumulative information indicating a value thataccumulate as a function is engaged; and the control unit transmits toand stores into the first storage unit the cumulative information in thesecond storage unit as a first function is engaged, and then resets thecumulative information at the second storage unit; the control unitreads the cumulative information stored in the first storage unit of thebattery unit from the battery unit as a second function is engaged; thecontrol unit obtains a sum of the cumulative information having beenread and cumulative information stored in the second storage unit afterresetting; and the control unit uses the sum of the cumulativeinformation thus obtained as new cumulative information to betransmitted to the battery unit.
 12. A camera according to claim 11,wherein: the control unit reads the cumulative information from thefirst storage unit as a function to be engaged first is engaged andtransmits the cumulative information to the first storage unit as afunction to be engaged last is engaged.
 13. A camera according to claim11, wherein: a plurality of functions include at least one of an imagephotographing function, a monitor display function, a light emittingillumination function, an AF function and a zoom function; and thecumulative information includes at least one of a number of images thatare photographed, an accumulated time length of monitor display deviceON time, a number of times light has been emitted for illumination, anaccumulated length of AF operation time and an accumulated length ofzoom operation time.
 14. A camera that operates on power supplied from abattery unit loaded therein having a chargeable secondary battery, ameasurement unit that measures remaining battery power value in thesecondary battery and a first storage unit in which the remainingbattery power value is stored, comprising: a function unit that executesa plurality of functions of the camera; a control unit; a second storageunit; and a display unit, wherein: the second storage unit storestherein cumulative information indicating values that accumulate as thefunctions are engaged; the control unit transmits to and stores into thefirst storage unit the cumulative information as a first function isengaged, and then resets the cumulative information at the secondstorage unit; the control unit reads the remaining battery power valueand the cumulative information from the battery unit as a secondfunction is engaged; the control unit reads the remaining battery powervalue as each of the plurality of functions is engaged, displays theremaining battery power value thus read at the display unit, and obtainsa sum of the cumulative information having been read and cumulativeinformation stored in the second storage unit; the control unit uses thesum of the cumulative information thus obtained as new cumulativeinformation to be transmitted to the battery unit.
 15. A camera systemcomprising: a battery unit having a chargeable secondary battery, ameasurement unit that measures remaining battery power value in thesecondary battery and a first storage unit in which the remainingbattery power value is stored; a camera that operates on power suppliedfrom the battery unit loaded therein; and a charge apparatus thatcharges the secondary battery of the battery unit, wherein: the cameraincludes a function unit that executes a plurality of functions of thecamera, a control unit, a second storage unit, and a display unit; thesecond storage unit stores therein cumulative information indicatingvalues that accumulate as the functions are engaged; the control unitreads the remaining battery power value as each of the functions isengaged and displays the remaining battery power value thus read at thedisplay unit; the control unit reads the cumulative information storedin the first storage unit as one of the functions is engaged; thecontrol unit obtains a sum of the cumulative information having beenread and the cumulative information stored in the second storage unit;the control unit transmits the sum to the battery unit for storage andalso resets the cumulative information at the second storage unit asanother function is engaged; and the charge apparatus resets thecumulative information stored in the first storage unit when thesecondary battery in the battery unit has been charged.
 16. Anelectronic apparatus system comprising: a battery unit having achargeable secondary battery, a measurement unit that measures remainingbattery power value in the secondary battery and a first storage unit inwhich the remaining battery power value is stored; an electronicapparatus that operates on power supplied from the battery unit loadedtherein; and a charge apparatus that charges the secondary battery ofthe battery unit, wherein: the electronic apparatus includes a functionunit that executes a plurality of functions of the electronic apparatus,a control unit, a second storage unit, and a display unit; the secondstorage unit stores therein information that is altered as the functionsare engaged; the control unit reads the information stored in the firststorage unit as one of the functions is engaged; the control unitgenerates the information with new content based upon the informationhaving been read and the information stored in the second storage unit;the control unit transmits the information with new content to thebattery unit for storage and also resets the information in the secondstorage unit as another function is engaged; and the charge apparatusresets the information stored in the first storage unit when thesecondary battery in the battery unit has become charged.